Method for taking finger impressions.



HAKoN. JORGENSEN, or COPENHAGEN, DENMARK.

METHOD FOR TAKING FINGER IMPRESSIONS.-

No Drawing.

To all whom it may concern v Be it known that I, HAKoN JORGENSEN,

' a subject of the Kingdom of Denmark, re-

siding at No. 16 Lyngbygade, Copenhagen, Denmark, have inventedcertain new and useful Improvements in Methods for Takmg Finger Impressions; and I do hereby declare the following to be a full, clear, and

exact description of the invention, such as will enable others skilled in the art to which it appertains to make and use the same.

This invention concerns a method for taking and preparing finger impressions, by

means of which methodit is possible to get much better impressions than by the usual method, because it is possible, by this new method, to get an impression of the entire tips of the fingers at once, without the necessity of turning the fingers during the process of taking the impression, and without fear of a displacement of the fingers on the paper.

According to the method hitherto used, the finger-impressions were taken in the following manner: The fingers were pressed against a polished-zinc plate evenly coated with printers ink, after which the thereby blackened finger-tips were pressed against a sheet of paper placed on a firm underlying surface. In order to get an impression of the entire finger-tips (i. e. the under and side surfaces of the finger-tips) by this old method, it is necessary to turn the fingers from one side to the other while taking the impression, and of course this easily impairs the accuracy of the impression, and furthermore the finger is also very easily displaced in taking the impression, which is thereby rendered less distinct. This defect is obviated by the new method, according to which the impression is not taken by means of.

printers ink but by means of a chemical liquid, which reacts on the properly prepared sheet of paper in such a manner that the portions of the surface of the paper which are moistened by'the liquid are discolored, while the impression is not taken against a -firm underlying surface, but it is either taken against a yielding underlying material into which the finger-tips are pressed in such a manner that not only the lower surface but also the sides of the fingertips -are simultaneously impressed without turning the fingers; or it is taken in such a manner that the surface of the paper is given' such a character through preparation that Specification of Letters Patent.

the finger-tips, when moistened with the chemical liquid, stick to it, so that the paper, when the finger-tipsare pressed against it, with the fingers held some distance apart, thereafter, by means of a lead-pencil, or the like, can be pressed against the lateral surface of the finger-tips, without fear of the paper thereby being dislocated. Consequently the whole procedure is very simple,

since, in order toftake an impression, it 1s only necessary to moisten the finger-tips with the liquid and then to press the finger: tips against the sheet of prepared paper. These sheets of paper may preferably be bound in asmall pocket note-book form and perforated at the back, so as to be conveniently torn off, and they may be suitably prepared on one side, for instance by coating them with a suitable gelatin solution, which,

when moistened by the liquid, becomes sticky and adheres to the fingers; while the other side of the sheets may preferably be coated with gum-arabic, so that, after they have been torn out .of the book and used for taking finger-impressions, they may be conveniently stuck on to a protocol, or the like;

A solution especially suitable for prepar ing the sheets of papermay, for instance, be' composed of 100 gr. French gelatin, 25 gr. Russian gelatin, 25 gr. glycerin,t5O gr.

Patented Feb. 1, 1916. Application filed October 8, 1914. Serial No. 865,719,

yellow prussiate of potash, 1 liter distilled water." The solution should be spread on the paper while hot., I

As already mentioned, the chemical liquid used must be of such a chara'cter'that it will react on the prepared surface of the paper, 71. e., discolor it wherever it is touched by the liquid, so that the papillary lines of the finger-tips will be sharply and plainly traced on the sheet of paper; for instance, blue impressions can be obtained on a sheet of paper prepared with a solution of gelatin, by using a liquid composed of 30 gr. of 25% solution of chlorid of iron, 10 gr. of a 25% solution of chlorid of lime, 10 gr. concentrated hydrochloric acid. The liquid is applied to the finger-tips by means of a tuft of cotton-wool, previous cleaning not being necessary. With the aforesaid gelatin solution the liquid gives quickly and evenly transferred to the paper on contact therewith.

The yielding; underlay, or bed, may be in the form ofii small cushion, whichmay be made of the so-called factis, well known in rubber manufacture.

Claims: I i I 1. The herein described method of taking finger impressions, which consists in treating fan impression-receiving surface with a substance capable of being rendered adhesive and of becoming discolored, applying to the fingers a substance adapted to chemically react with said first named substance to discolor and render the same adhesive, when coming in contact with it, and finally efiecting contact between the fingers and said im pression-receiving surface. I

2. The herein-described method of taln'ng finger impressions, which consists in treating a yielding impression-receiving surface with other surface of said paper blank with asubstance capable of being rendered adhesive, applying to the fingers a substance adapted to chemically react with said first named substance to discolor and render the same adhesive when coming in contact with it, and finally eflecting contact between the fingers and the surface of the paper blank treated with said first named substance.

4. The herein described method of taking finger impressions which consists in treating animpression -receiying surface with a solution comprising French gelatin, Russian gelatin, glycerin, y'ellow prussiate of potash and water substantially in the proportions specified, applying to the fingers a substance adapted to chemically react with the said solution to discolor and render the same adhesive, when coming in contact with it, and finally effecting contact between the fingers and said impression-receiving surface.

5. The herein described method of taking finger impressions which consists in treating an impression-receiving surface with a substance capable of being rendered adhesive and of becoming discolored, applying to' the fingers a solution adapted to '-chemically react-with said substance when coming in contact with it, and comprising chlorid of iron, chlorid of lime and concentrated hydrochloric acid substantially in the proportions specified, and finally efiecting contact between the fingers and said impression-receiving surface.

6. The herein described method of taking fingerimpressions which consists in treating a yielding impression-receiving surface with a solution comprising French gelatin, Russian gelatin, glycerin yellow prussiate of potash and water su stantially in the proportions specified, applying to the fingers a solution comprising chlorid of iron, chlorid of lime and concentrated hydrochloric acid substantially in the proportions specified, and finally conforming said impression-receiving surface to and in conic tact with the fingers.

In testimony whereof, I afiix my signa ture.

HAKON J ORGENSEN. 

